The present invention relates to a flow completion apparatus for producing oil or gas from a subsea well. More particularly, the invention relates to a flow completion apparatus which comprises a tubing hanger having an annulus bore which is adapted to communicate with a choke and kill line of a blowout preventer which is installed over the tubing hanger during installation and workover of the flow completion apparatus.
Flow completion assemblies for producing oil or gas from subsea wells may generally be categorized as either conventional or horizontal. A typical horizontal flow completion assembly is disclosed in U.S. Pat. No. 6,039,119, hereby incorporated herein by reference.
International Publication No. WO 01/73259 of International Application No. PCT/US01/09607 filed Mar. 22, 2001 and published Oct. 4, 2001, shows a tubing hanger with an annulus bore. International Publication No. WO 01/73259 is hereby incorporated herein by reference.
The flow completion apparatus comprises a wellhead housing which is installed at the upper end of the wellbore; a tubing spool which is connected over the wellhead housing and which includes a central bore which extends axially therethrough, a production outlet which communicates with the central bore, and an annulus passageway which communicates with the tubing annulus; a tubing hanger which is supported in the central bore and is connected to an upper end of the tubing string, the tubing hanger including a production bore which extends axially therethrough and a production passageway which communicates between the production bore and the production outlet; a first closure member which is positioned in the production bore above the production passageway; production seals positioned between the tubing hanger and central bore above and below the production passageway; and a tubing annulus seal which is positioned between the tubing hanger and the central bore below the production passageway and production seals. Furthermore, the tubing spool also comprises a workover passageway which extends between the annulus passageway and a portion of the central bore that is located between the production seals and the tubing annulus seal, and the tubing hanger also comprises an annulus bore which extends between the workover passageway and the upper end of the tubing hanger. In this manner, fluid communication between the tubing annulus and the upper end of the tubing hanger may be established through the annulus passageway, the workover passageway, and the annulus bore.
The flow completion apparatus further comprises a blowout preventer which is removably connectable to the top of the tubing spool and which includes a BOP bore, at least one set of BOP rams, and at least one choke and kill line that communicates with a portion of the BOP bore which is located below the BOP rams; and a tubing hanger running tool which is removably connectable to the top of the tubing hanger and which includes a generally cylindrical outer diameter surface and a production port that communicates with the production bore in the tubing hanger. An annulus passageway extends between the annulus bore in the tubing hanger and the BOP choke and kill line. This passageway may either be the annular area around the tubing hanger running tool or may include an annulus port through the running tool that communicates between the annulus bore and an opening which is formed in the outer diameter surface of the tubing hanger running tool to communicate with the BOP choke and kill line. In this manner, fluid communication between the tubing annulus and the BOP choke and kill line may be established through the annulus passageway, the workover passageway, the annulus bore, either the annular area around the tubing hanger running tool or an annulus port in the tubing hanger running tool, and the portion of the BOP bore which is located below the closed BOP ram.
The annulus bore in the tubing hanger provides a convenient means for connecting the tubing annulus with the BOP choke and kill line. An annulus port in the tubing hanger running tool provides a closed path between the annulus bore in the tubing hanger and the BOP choke and kill line.
A first barrier between the wellbore and the environment is provided by both the first closure member in the production bore and the tubing annulus seal between the tubing hanger and the tubing spool. In addition, a second barrier between the wellbore and the environment is provided by both a second closure member that is positioned in the production bore above the first closure member and the production seals that are positioned between the tubing hanger and the tubing spool above the tubing annulus seal. In this manner, both the first and second barriers between the wellbore and the environment are mounted in or on the tubing hanger.
These and other objects and advantages of the present invention will be made apparent from the following detailed description, with reference to the accompanying drawings. In the drawings, the same reference numerals are used to denote similar components in the various embodiments.